Haplocheirus – Is it a bird? No, it is a Dinosaur

Haplocheirus – Ancient Alvarezsaurid from China

The Alvarezsaurids, a bizarre and little known group of swift, cursorial (running) dinosaurs have puzzled scientists since fossils of these unusual creatures came to light in the 1990’s. Are they birds, or are they dinosaurs? These animals show features of each, for example, bird-like features include a deep keel in the chest and specialised forelimbs, fused ankles and a narrow skull. These animals were presumably covered in downy feathers and with their long beaks and long legs they would have resembled storks. However, they possessed a long tail, presumably to balance them as they ran and a bizarre, huge, single claw on the end of each hand.

Originally, known from Cretaceous strata from South America, it was thought these animals were an off-shoot of the Aves (Birds). They could not fly but seem to have evolved to be fast running insectivores, perhaps using their short, but strong arms and powerful claw to break into termite nests.

Whether they were birds or members of the Dinosauria is debated, however, the discovery of the fossils of a Alvarezsaurid from the mid Jurassic has swung the debate in favour of declaring Alvarezsaurids as true dinosaurs.

A dinosaur fossil discovered in north-western China and reported upon in the scientific journal “Science” has provided fresh evidence that although Alvarezsaurs resembled birds, they must have evolved separately – helping confirm that modern birds are indeed living dinosaurs.

The 160 million year old fossils, (Callovian faunal stage), were found in north-western China, in a region from which many Jurassic dinosaur fossils have been discovered. This primitive Alvarezsaur, which has been named Haplocheirus sollers (means “simple, skilful hand”), has the classic short forelimbs and large claws of this particular type of dinosaur, but because it dates from before the time of the first known bird (Archaeopteryx), it gives credence to the theory that Alvarezsaurs are dinosaurs and not birds.

An Artist’s Impression of Haplocheirus sollers

Picture Credit: Portia Sloan/Science Magazine

The illustration shows H. sollers covered in downy, insulating feathers, with long legs, strong arms and three-fingered hands. The first fossils of Alvarezsaurus when excavated in South America were illustrated as having three-fingered hands, typical of a Coelurosaurid dinosaur, however, a more complete fossil of a Alvarezsaur excavated in China, showed that these animals had a single, powerful digit on each hand.

Haplocheirus sollers had a deep keel, and three toes on each foot, it walked in a digitgrade stance just like modern birds, but at nearly 3 metres long, (mostly tail), it was a size-able dinosaur.

The author of the scientific paper was Jonah N. Choiniere, a member of a team of researchers from George Washington University that had worked on the fossil excavation in collaboration with Chinese scientists.

Classified as an Alvarezsaur, the only Jurassic representative of this family known it pre-dates the first bird Archaeopteryx by at least ten million years.

Commenting on his work, Jonah stated:

“Although it certainly couldn’t fly, the members of this group were originally thought to be birds. Although they’re closely related to birds, they clearly weren’t birds at all.”

When in the past many fossil-hunters believed that the Alvarezsaur dinosaurs were in fact birds – and some still believe it – they argued that because those so-called birds had appeared in the fossil record at the same time as dinosaurs, the birds could not have been descended from them.

But Kevin Padian, a noted palaeontologist and dinosaur expert at UC Berkeley, said the new specimen is important because it shows definitely that Choiniere’s dinosaur and its relatives had evolved quite separately from the ancestors of birds.

“This is another salvo that blows apart the claims of the ‘birds are not dinosaur’ crew,” he commented.

It seems we have a lot more to learn about the bizarre Alvaresaurids. However, with fossils of this type of dinosaur located in places as geographically and chronologically separate as mid Cretaceous strata in South America and mid Jurassic rock formations from north-western China, one thing is for sure – these dinosaurs were a very successful and widespread group.